Resurrecting Hubble

Tuesday

But when it breaks down, the 18-year-old space telescope is an orbiting question mark that punctuates concerns about NASA mission priorities, money and astronaut safety.

When it works, the Hubble is an astronomical wonder.

But when it breaks down, the 18-year-old space telescope is an orbiting question mark that punctuates concerns about NASA mission priorities, money and astronaut safety.

A week ago today, the space agency was supposed to launch a space shuttle to repair a host of problems that astronauts spent months training to fix.

But that mission was scrapped when a computer that gathers and sends scientific data from the Hubble to Earth shut down. Last week, NASA attempts to fire up a backup computer failed.

"We no longer have the ability to communicate with the scientific instruments," said Mike Weiss, deputy associate director for the Hubble Program at the NASA Goddard Space Flight Center in Maryland.

NASA says the timing of the computer failure was fortuitous. If it had died a week after the shuttle mission was completed, the service project could have been in vain.

For scientists, there is no question: This icon must be saved.

"This is a really critical component; it's the main manager for the instruments," said Brad Peterson, chairman of the Ohio State University's astronomy department. "This bubbles up to be one of the highest priorities."

Peterson is a member of the Space Telescope Science Institute Council, which helps choose Hubble science programs and grants.

Like others, he is eager for NASA to come up with plans to keep Hubble humming.

When it comes to discoveries, Hubble has hit more home runs than Hank Aaron.

From its 375-mile-high perch, it has accurately estimated the age of the universe, produced the first details of planets around other stars and provided evidence that expansion of the universe is accelerating.

The images it has sent back are stunning, giving scientists clear views of galaxies they could only dream of. Thousands of scientific papers have flooded astronomy journals.

But from the start, it has been a bit of a fixer-upper. There have been three service missions since it was launched.

After last week's scrubbed mission, NASA has penciled in Feb. 12 to launch the next repair crew and add replacing the Science Command and Data-Handling Computer to the list.

Weiss said there is good news: NASA has a backup computer, built when Hubble was launched, at the Goddard site.

"It was designed from the get-go to be replaced," Weiss said.

NASA estimates that the computer swap will take 90 minutes. Not all the tasks, however, are so simple.

After the shuttle Columbia exploded during its return to Earth in 2003, NASA canceled a scheduled fourth service mission over safety concerns. But Congress saved the mission, largely because of the potential for new discoveries.

"After Columbia, we reviewed everything, questioned all our assumptions and developed new techniques," said Atlantis crew commander Scott Altman.

During a week in space, the crew will swap out computers, electronics and cameras and make technical repairs unlike any performed in the past.

"Every time astronauts go up to work on Hubble, (we hold) our breath because we have so much invested," said Chris Mihos, a Case Western Reserve University astronomer who studies the origin and evolution of galaxies.

He said that although the instrument now works in concert with the Spitzer infrared and Chandra X-ray telescopes, "in terms of science, (the Hubble) is still the flagship."

What makes this mission even more difficult is that, before Atlantis can go up, a second shuttle must be on standby so it can launch and serve as a rescue vehicle if needed.

The shuttle Discovery will be the backup in February, said Chuck Shaw, director of Hubble servicing missions.

Altman and shuttle pilot Gregory Johnson have been training for months.

"I can honestly say, if I could choose, I'd have chosen this mission because it has such a scientific payoff," Johnson said. "If everything works -- and that's an 'if' -- its discovery power will be over 10 times its current power."

On the third day of the mission, Altman will ease Atlantis beneath the Hubble so the shuttle and telescope will orbit at the same speed: nearly 18,000 mph.

With bay doors wide open, Megan McArthur will reach with the space arm, grab hold of Hubble and secure the 40-foot telescope.

Then the repairs begin. Astronauts have been practicing on mock-ups and underwater, to simulate weightlessness.

Five space walks are planned. Each could last 6 1/2 hours.

The first chores likely will be replacing the science data computer and the Wide Field Camera.

During the second walk, an instrument called the Cosmic Origins Spectrograph is scheduled to be installed. The spectrograph will help scientists learn how carbon and iron first formed and how they helped shape the galaxies, stars and planets.

The astronauts will work as a surgical team to fix the Advanced Camera for Surveys, the shuttle's workhorse camera.

With both power supplies dead, and limited time for repairs, the astronauts will wire in a new power supply.

To get to there, astronaut John Grunsfeld will have to remove 36 small screws and washers, some of which he can't see. He'll be working around a corner in a bulky, stiff space suit.

He'll wear an old pair of gloves that allow a little more finger movement.

"Even if we fail, which we won't, Hubble will continue to do great science," Grunsfeld said.

Astronauts Michael Good and Michael Massimino will crawl inside Hubble and replace all six gyroscopes that are used to point the telescope.

They'll also replace a 450-pound battery that's worked since 1990 to power the Hubble when the sun can't.

Then the two will repair the Space Telescope Imaging Spectrograph that breaks down light to help scientists determine what elements are in or surround stars, their temperatures and their motion.

The power supply and backup are both down.

"To get to the power supply, we have to remove a panel with 111 screws and washers that are not captive or magnetic," Good said.

Goddard engineers created a plexiglass cover that has holes large enough to allow the head of the power screwdriver through, but too narrow for a screw or washer to pass through.

Once the panel is off, the astronauts will replace a computer card, then replace the panel itself with one that has latches instead of screws.

To Good, his biggest fear is debris. He worries that whatever gets out could mar the telescope's mirror.

"It'll be a smudge on every picture Hubble sends back to Earth," Good said.

kmayhood@dispatch.com

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